1. Field of the Invention
The present invention relates to an intake control system for an engine that achieves improved output performance over low and high speed rotational ranges.
2. Background Art
A conventional intake control system, in which a relief valve automatically opens in response to a differential pressure across upstream and downstream sides of the relief valve, is used to prevent excessively lean air/fuel ratios. This type of device is shown in Japanese Patent Laid-open No. Sho 58-155270.
In such an intake control system, when the engine is rapidly accelerated in response to the rapid opening of a throttle valve, an intake air amount is restricted by a small air hole provided on the relief valve. The relief valve is used to suppress the leaning of the air-fuel ratio of a mixture prior to entering the combustion chamber, thereby achieving improved acceleration performance.
The relief valve of the conventional system prevents rapid inflows of intake air by restricting air intake at the air inlet to the air cleaner. The relief valve automatically opens when a differential pressure across the upstream and downstream sides of the relief valve exceeds a specific value. In a high speed rotational range, the relief valve is opened due to the increase in the air intake amount over the specific value.
However, the above-described prior art system demonstrates the following shortcoming. The conventional system utilizes a relief valve that is biased by a spring force in the valve closing direction. The spring force acts as the air intake resistance that restricts the opening of the relief valve.
The present invention overcomes the shortcomings associated with the prior art and achieves other advantages not realized by the prior art.
An object of the present invention is to provide an intake control system for an engine which is capable of reducing air intake resistance in a high speed rotational range of the engine and thereby improves the output performance of the engine.
A further object of the present invention is to provide an intake control system for an engine which is capable of reducing air intake resisistance in a high speed rotational range, while still preventing the leaning of air/fuel ratios of a mixture while operating in a low speed rotational range.
A further object of the present invention is to use a spring force and air intake pressure to bias an air intake valve in the closed position.
These and other objects are accomplished by an intake control system for an engine comprising: a plurality of passages disposed in parallel and formed in an air cleaner; an intake control valve for opening/closing at least one passage of said plurality of passages is provided in said air cleaner; and an actuator for closing said intake control valve in a low speed rotational range of said engine and opening said intake control valve in a high speed rotational range of said engine is connected to said intake control valve.
These and other objects are further accomplished by an intake control system for an engine comprising: an air cleaner; a plurality of throttle bodies each having an intake passage; a plurality of air funnels for connecting to the intake passages of the throttle bodies; a cleaner case including a lower case half and an upper case half; an element mounting plate for partitioning an inside of the cleaner case into a lower side dirty air chamber and an upper side clean air chamber; a cleaner air element mounted in a mounting hole provided in the element mounting plate; a partition wall for partitioning the lower side dirty air chamber into a plurality of passages disposed in parallel and formed in an air cleaner; and an intake control valve for opening/closing at least one passage of said plurality of passages is provided in said air cleaner, wherein said intake control valve is closed in a low speed rotational range of said engine and opens in a high speed rotational range of said engine.
These and other objects are also accomplished by an engine for mounting on a motorcycle, said engine comprising: an electronic control unit; at least one combustion chamber; a cylinder block; a cylinder head; an exhaust control system; and an intake control system, said intake control system including a throttle body connected to said engine; an air cleaner for cleaning air flowing in an intake passage of said throttle body is disposed on an upper portion of said engine; and said air cleaner includes a cleaner case and a cleaner element for partitioning the inside of said cleaner case into a dirty air chamber in communication with atmospheric air and a clean chamber in communication with said intake passage of said throttle body; said clean chamber disposed in said cleaner case on an upper portion of said dirty air chamber; and an intake control valve for opening and closing at least one passage of said plurality of passages is provided in said cleaner case; a partition wall for partitioning an intermediate portion of said dirty air chamber into a plurality of passages disposed in parallel is provided in said cleaner case; and an actuator for closing said intake control valve in a high speed rotational range of said engine and opening said intake control valve in a high speed rotational range of said engine is connected to said intake control valve; wherein said engine is capable of being mounted on a motorcycle so that said cylinder block and said cylinder head are tilted in a forward direction of the motorcycle.
With the first feature, in the low speed rotational range of the engine, the intake control valve is held, by the actuator, in a state in which at least one of the plurality of passages is closed, so that the amount of an intake air passing through only the other passage is restricted upon rapid opening of the throttle valve. As a result, it is possible to suppress the leaning of an air-fuel mixture sucked in the engine, and hence to achieve a good accelerating performance of the engine.
When the operational state of the engine is shifted to the high speed rotational range, the intake control valve is positively opened by the actuator, so that air sucked in the engine can pass through not only the one passage not obstructed by the intake control valve but also the other passage. As a result, it is possible to effectively reduce the intake resistance and increase the volumetric capacity of the engine, and hence to achieve the high output performance of the engine.
According to a second feature of the present invention, there is provided an intake control system for an engine mounted on a motorcycle in which an engine is mounted on a body frame with a cylinder block and a cylinder head thereof kept in a forward tilting posture; a throttle body is connected to the engine; an air cleaner for cleaning air flowing in an intake passage of the throttle body is disposed on the upper portion of the engine; and the air cleaner includes a cleaner case and a cleaner element for partitioning the inside of the cleaner case into a dirty air chamber communicated to atmospheric air and a clean chamber communicated to the intake passage of the throttle body.
The intake control system is characterized in that the clean chamber is disposed, in the cleaner case, on the upper portion of the dirty air chamber; the intake passage of the throttle body is communicated to the clean chamber; a partition wall for partitioning an intermediate portion of the dirty air chamber into a plurality of passages disposed in parallel is provided to the cleaner case; an intake control valve for opening/closing at least one of the plurality of passages is provided to the cleaner case; and an actuator for closing the intake control valve in a high speed rotational range of the engine and opening the intake control valve in a high speed rotational range of the engine is connected to the intake control valve.
With this second feature, in addition to the improved output performance of the engine like the first feature, since the layout of the components in the cleaner case, i.e. the layout of the plurality of passages, the intake control valve, and the portion communicated to the intake passage of the throttle body, is practical, it is possible to make a more compact air cleaner and to easily position the air cleaner on the upper portion of the engine without limiting engine orientation or mounting positions.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.